I have an amide-containing compound, and I would like to show that it is undergoing hydrogen bonding with a polar aprotic solvent. Can this be done with FT-IR?
Yes it can, furthermore very easy, cheap and fast. You should prepare set of solvent mixtures with different ratio of your aprotic solvent, for example CH3CN in CHCl3, CCl4 or CS2 (ca. 10 mixtures). Than in those solvent mixtures you should dissolve your amide and to evaluate fast H-bonding scheme.
Please pay attention to both spectra in TEA with different concentrations in CHCl3 of 4AP as attachment (related ref. 1). You can evaluate in this case HNH...N hydrogen bonding of NH2 - group in 4AP.
[Ref. 1] Arnaudov, M.; Ivanova, B.; Dinkov, S. (2004) A reducing-difference IR-spectral study of 4-aminopyridine, Central European Journal of Chemistry 2, 589-597.
"Hydrogen bonding of an amide-containing compound with a polar aprotic solvent" is an extremely ambiguous question: What is the H-bond donor (HBD) and the H-bond acceptor (HBA)?
The amide carbonyl is a strong HBA (base), but primary and secondary amides are also HBD (acids), resulting in self association; only at very high dilution the dimers (oligomers...) may be dissociated. Tertiary amides can be considered as purely HBA.
As the question concerns H-bonding with an "aprotic solvent" I suppose that the solvent is "non-HBD" (this is not the case of CHCl3). CH3CN is HBA, asall polar solvents, but CCl4 and CS2 (both toxic!!!) are both non-HBD and non-HBA (almost).
If you can give more details on your system, I'll be glad to continue our discussion.
By the way, FT-IR is a very good technique for detection and quantitative measurement of H-bonding. Depending on the concentration you may need special cuvettes (longer optical path for dilute solutions, a pair of cuvettes if solvent compensation is needed...). My colleague Christian Laurence (emeritus, U. Nantes, France) published a lot of papers on the matter (we have published a book including these data). Extensive scales of H-bond strength were devised this way, using equilibrium constant measurement or simply the shift of the stretching frequency of the X-H bond implied in the association.
Jean, thanks for your reply. The solvent is DMF, which I imagine can only act as a HBA. If my understanding is correct, FT-IR could show me that the amide is undergoing some type of hydrogen bonding, but it can't show me if it is hydrogen bonding to a given molecule (i.e., self-association vs. HB to a solvent molecule).
Shifting in the peak position or sometimes broadening are generally marker for the hydrogen bond formation in solvent. Red or blue shift during the hydrogen bond formation is depending on the charge distribution. You can also do Raman measurements. The solvent induced wavenumber shifts of Raman bands provide useful information regarding the solute-solvent interaction.
Nicholas, you are right, DMF can only act as a base or HBA (neglecting very weak interactions involving C-H bonds). The H-bonding to the carbonyl may be observed by a shift of the C=O stretching mode (decrease of the wavenumber), but the change may be small depending of the interaction, and also because the solvent is in great excess (high dilution) and only a small fraction of the DMF molecules is involved. The most significant changes will be seen on the X-H mode of the HBD, but in case of a complex molecule (polyfunctional...) there may be a competition with inter- or intramolecular H-bonding and bonding to solvent. If you change the solvent (weakest HBA than DMF) a change in the X-H absorptions could be an indication of the specific effect of DMF. NMR may be also an interesting tool. The H-1 spectra of the involved protons are evidently a good probe of H-bonding. Remember that the shift of the NMR H-1 signal is a time-averaged mean of the chemical shifts of the various species. On the contrary, IR shows a different spectrum for each species, when the differences in spectra are sufficient (resolution may be also an issue).